Parking meters permit vehicles to be parked on streets for an allowable time determined by the number and denominations of coins which are placed in the parking meter. A clock mechanism in the parking meter runs down the allowable time until it reaches zero, and an overtime parking indication appears.
The coin receiving devices of the parking meters perform various tests to determine whether an acceptable coin has been inserted, and the denomination of the coin. Circuitry which tests for the presence of the ferrous material (i.e., slugs) includes Hall-effect sensors, and frequency shift metallic detectors. The denomination is determined by devices which measure the diameter of the coin such as infra-red emitting diodes and photodiodes, or which measure the weight of the coin using strain gauges, and the like.
Coin receiving mechanisms which use IR detectors, Hall-effect circuitry, magnetic fields and light sensing rays with microprocessors include U.S. Pat. Nos. 4,460,080 (Howard); 4,483,431 (Pratt); 4,249,648 (Meyer); 5,097,934 (Quinlan Jr.); 5,119,916 (Carmen et al.).
In recent years, electronic parking meters and systems have been developed which use microprocessors in conjunction with electronic displays, IR transceivers to communicate with auditors, and ultrasonic transceivers to determine the presence of vehicles at the parking meter. U.S. Pat. Nos. 4,967,895 (Speas) and 4,823,928 (Speas) disclose electronic parking meters which use microprocessors, electronic displays, IR transceivers, solar power and sonar range finders. In addition, British Publication No. 2077475 also discloses a low power electronic parking meter that operates using solar cells.
The sophisticated devices which use microprocessors, electronic displays and IR/ultrasonic transducers consume too much power to operate by non-rechargeable batteries alone. Thus, the Speas' patents disclose the use of solar power cells which charge capacitors or rechargeable batteries.
Various problems exist with the use of solar power sources including the use of parking meters in shady areas, or the use of parking meters during periods in which there is very little sunlight. This causes the rechargeable batteries to run down, and they require frequent replacement. Or, in the case of the use of capacitors, the lack of power causes the meter to become inoperative.
Low power coin sorters are disclosed in U.S. Pat. Nos. 4,848,556 (Shah et al.); 5,060,777 (Van Horn et al.).
Coin processing and related auditing data systems are shown in U.S. Pat. Nos. 5,259,491 (Ward II); 5,321,241 (Craine); 5,366,404 (Jones);
Other token/coin processing devices such as disclosed in U.S. Pat. No. 3,211,267 (Bayha) provides token validation using magnetics; U.S. Pat. No. 3,998,309 (Mandas et al.) discloses an apparatus to prevent coin stringing and U.S. Pat. No. 5,062,518 (Chitty et al.) discloses apparatus that detects coin denomination based on acoustic vibrations from the coins striking an internal surface.
Parking devices using wireless data transmission are disclosed in U.S. Pat. No. 4,356,903 (Lemelson et al.); U.S. Pat. No. 5,103,957 (Ng et al.); U.S. Pat. No. 5,153,586 (Fuller); U.S. Pat. No. 5,266,947 (Fujiwara et al.).
Furthermore, the electronic parking meters are not necessarily intelligent meters. That is, these meters use electronics but they do not respond to changing conditions. For example, none of the above devices resets the parking meter to an expired state should the vehicle leave before the allotted time has passed; instead, the parking meter provides "free" parking for the time remaining.
In U.S. Pat. No. 5,407,049 (Jacobs), U.S. Pat. No. 5,454,461 (Jacobs), and application Ser. No. . 08/300,253 all of which are assigned to the same Assignee of the present invention and all of whose disclosures are incorporated by reference herein, there is disclosed a low-powered electronic parking meter that utilizes, among other things, a sonar transducer to detect the presence of vehicles, an infra-red transceiver for communicating with parking authority personnel, and domestic coin detection, coin jam detection and slug detection.
However, not all electronic parking meters that utilize some type of microprocessor, microcontroller or other digital processing have the capability of detecting the presence of vehicles.
Therefore, there remains a need for an easily-attachable and secure accessory unit to any electronic parking meter in order to provide that electronic parking meter with the ability to detect the presence of vehicles without the need to substantially modify the hardware of the electronic parking meter.